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3857 |
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Friday, May 23, 2014, Hall A 10:00 AM Medical Industry 1 |
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Mechanical study of novel VPS-titanium coating of polyethylene for orthopaedic implants |
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Laurent Corté* / Mines ParisTech
Centre des Matériaux, France Géraldine Wolinne / Mines-ParisTech, Centre des Matériaux, CNRS UMR 7633, France Michel Jeandin/ Mines-ParisTech, Centre des Matériaux, CNRS UMR 7633, France Sylvie Ruch/ Alhenia AG, Switzerland Armando Salito/ Alhenia AG, Switzerland |
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Polyethylene is a prominent biomaterial, that is particularly relevant for osteoarticular prosthetics. Nevertheless, its hydrophobicity hinders cell adhesion and surface treatments are often required to produce a proper anchorage to bone tissues. The use of osteoconductive porous titanium coatings is a promising solution to overcome this limitation but suitable adhesion of titanium onto such organic substrates is uneasy to achieve. Recently adherent titanium coatings having the suitable level of porosity for osteoconduction have been obtained by novel VPS-based methods and may meet great expectations. This study reports the first experimental characterization of the strength and adherence of these titanium coatings on polyethylene substrates. Differential scanning calorimetry and nanoindentation show that the polyethylene is melted and recrystallized during the coating process within a layer of about 300µm thickness. Bending tests coupled to microscopic observations including in situ bending tests in SEM show the existence of a critical tensile strain of about 1% corresponding to the onset of the first cracks in the coating. As the strain increases above this value, the crack density increases in the coating without any noticeable debonding up to large strains exceeding 10%. Fatigue bending tests carried out over a million cycles reveal that the coating remains uncracked under this critical strain and stays in a stable cracked state without debonding above it. Moreover, a whole characterization protocol for advanced LASER Shock Adhesion Testing (LASAT®) on this type of material system was developed. The first tests captured the existence of a debonding threshold corresponding to the coating-substrate adhesion strength. These results confirm the promising potential of VPS-based titanium coatings for the surface treatment of polyethylene prostheses. More generally, they open the way for further systematic measurements, which would involve both experiments and simulations and provide a thorough and quantitative characterization of titanium coating adhesion onto polyethylene. |